This invention relates to a method and apparatus for cooling the primary gas produced in the gas generator having a vertical shaft operating under pressure at a high temperature wherein the hot primary gas produced in the gasification region is discharged vertically into an after-gasification region, both of which includes lining of cooling tubes extending to an upper cooling region having walls containing means for tangentially introducing a cooling gas into the stream of hot primary gas.
When finely-divided solid fuel is gasified, for example, at a high temperature in the slag bath generator, the fuel is injected together with a gasifying medium in the form of, for example, oxygen, steam or CO.sub.2, by a set of nozzles into a melting chamber located within the lower portion of the gas generator. During the gasification process, the bottom of the melting chamber is covered with a liquid slag bath formed from the mineral constituents of the fuel. The resulting gases liberated during the gasification process consist chiefly of carbon monoxide and hydrogen. Gas generators of this type are usually operated at temperatures at which the slag is liquid. The liquid slag covering the bottom of the vertical reactor shaft flows toward and is discharged through a central overflow at the same rate as the slag is formed. The slag bath is kept in circular motion by a system of tangentially-arranged nozzles used to introduce fuel and a gasification agent. The bath of liquid slag forms a heat shield used to obtain very high flame temperatures. Strong turbulence in the rotating solid-gas phase above the radiating slag bath results in a rapid exchange of the gas film adhering to the solid fuel particles and accelerates the reaction due to the high temperature environment. The rising stream of very hot gas entrains a considerable amount of mineral fuel constituents in a pasty or molten form. The stream of gas initially flows vertically through an after-gasification region which is lined with cooling tubes. In an adjacent cooling region, cold gas which can take the form of cooled, purified production gas, is tangentially introduced at speeds between 20 and 40 meters per second. During this process, the cooling gas is subjected to centrifual and gravitational acceleration. The streams of cooling gas move along the container wall and follow spiral tracks downwardly. The cooling gas mixes with the rising hot primary gas, losing density through heat exchange. When the density of the cooling gas is adequately lowered, it is entrained by the primary gas which has been correspondingly cooled.
In this process, two faulty conditions occur. The first condition is erosion to the container wall by dust particles. This erosion occurs because the cooling gas is introduced at a high tangential speed to insure adequate mixing with the hot primary gas. Dust particles from the hot primary gas enter the stream of cold gas, thus causing the erosion to the container wall. The second condition is burning of the container wall by solidifying mineral constituents entrained in the hot primary gas. The mineral constituents burn on the container wall because when the cooling gas gradually loses tangential speed during its descent along the vertical shaft, the hot rising primary gas tends to travel around the edge of the cooling gas stream so that the solidifying mineral constituents entrained in the hot primary gas are brought into contact with the container wall and burn.